Fluid heaters



2 Sheets-Sheet l mn nzun. DDDDU J. KQLLING FLUID HEATERS March 4, 1958 tFiled Jan. so, 195s.

` INVENTOR v J5/:arm jl/oL//ing d ATTORNEY UDUUD DDEE D man E am .im @fwhun March 4, 1958 A.1. KoLLlNG 2,825,332

FLUID HEATERSA Filed Jan. 5o, 195s 2 sheets-sheet 2 INVENTOR .toward themiddle.

United States PatentfO FLUID HEATERS Johann Kolling, Oberhausen,Germany, assignor'toThe Babcock & Wilcox Company, New York, N. Y., a

corporation of New Jersey Application January 30, 1953, Serial No.334,221

4 Claims. (Cl./122-333) 'Ihe presentv invention relates in general. `toan improved construction of a iiuid heater .having a verticallyelongated furnace chamber with fuel burning means in the lower partthereof, and a laterally extending convection heating pass at its upperend;V and, more particularly, to an improved form of gas flow baie meansin the furnace chamber subjacent to the convection heating pass in aiuid heater of the character described which are arranged to moreuniformly distribute the-heating gases flowing from the furnace acrossthe fluid heating surfaces positioned in the heating pass, andcooperating with a special arrangement of tubes in a tube bankarrangedacross theentrance to said heating pass.

In Yfluid heaters of the character described, therev is a .tendency formost of the highest temperature heating a slag-forming fuel is burned.This is particularly evident with a furnace chamber having more thanfour lateral vertical walls which are symmetrically arranged to form afurnace of varying width and depth relative to its transverse centerlines'and from which the combustion gases flow laterally out of a gasexit opening whose width yis equal to the maximum width of the furnacechamber. In suchfa case not only the hottest but also the greatestquantity of the combustion gases are pressed This unequal temperaturedistribution of the gases tends to remain until the gases flow past thelast uid heating surface in the convection heating pass. This uneven gas.flow `is particularly undesirable where .vapor superheating tubes aredisposed-in the cons n vection heating pass, because localized gashotfspots tend v Ltoresultintube failure.

. Thejmainobject of my invention is'Y the provision of an improvedconstruction and arrangement of. thefurnace chamber in a fluid heaterofthecharacter .described for controlling the distribution of theheating 'gases .across the width of thevconvection heating pass` byreducing the amountof lhigh temperature gases flowing. through'the`middle portion of the furnace chamber. v

l A more yspecific object is the `provision ofla `furnace nose arch orbaffle subjacent.to the -lateral'lconvection :heating pass and, having amiddleV portion which` projects Ninwardly. toa greaterextent thaniitsside portions, thereby Ycorrespondingly reducing the gas.. owz .area in.the

These gases flow upwardly .at a `greater l ice ,2 distribution acrossthe width 'of vthe'convection heating pass. s

For a better understanding of the invention, itso'pe'r'ating advantagesand yspecific objects attained by'its use, vreference should be hadtothe 'accompanying' .drawings and descriptive matter in` which I haveillustrated and described a preferred embodiment of myfinve'ntion.

Of the drawings:

Fig. vl is a sectional elevation taken on the line 1--1 of Fig. 2 of asteam generating unit constructed in accordance with my invention; and

Fig. 2 isa horizontal cross-section taken'on theli-ne 2-2 of Fig. 1. n y

While in its broader aspects myfinvention is adapted for use in fluidheaters of the general character described,

Vit is particularly designed for-use lin uid heaters having a furnacechamber with more than four vertical side walls. In the steam generatingvunit illustrated, for example, the vertically elongated furnace chamber1 is an equi-lateral Octagon in horizontal cross-section. ln each of thewalls 3, 4, 5, 6, 7, 8, 9 and 10 is arranged a fluid fuel burner `2,whose axesv of discharge are symmetrically arranged tangent to animaginary circle about the furnace chamber axis. These burners arevsimilarly offset in the corresponding side Walls so that they dischargeyin the same angular direction relative to the circle. The furnace wallsare lined with steam generating Vtubes throughout their height. The rearwalls 7, 8 and 9 and corresponding wall tubes are inclined forwardly andthen rearwardly at their upper ends to form a wedge-shaped wall or archstructure 11, which defines a throat 24 adjacent the upper end of thefurnace chamber and the inclined bottom 25 of a convection heating pass26 extending laterally from the Vfurnace chamber `gas outlet 12. Thetubes lining the walls 7, 8 and 9 are connected at their upper ends toan intermediate header 14 extending across the bottom of the gas pass26. The tubes 15 lining the walls 7 and 9 have vertical upper endportions 16 forming corresponding vertical rear -wall sections 'of thethroat 24. A vertical screen bank of steam generating tubes .13 extendsupwardly from the header 14 to an external transverse steam and waterdrum 21. A pendant type bank of multiple looped steam super-heater tubes22 extends uniformly across the gas pass 26 rearwardly of the screenbank 13. The front walls 3, 4 and 5 extend upwardly above the level ofthe throat 24 and thenat `a rearward inclination to form a furnace roof27 substantially parallelto the inclined bottom y25 and extending acrosslthe upper end portion of the tubes 13 .to join the roof 28 of theconvection gas pass along the rear side of the drum 21.

- With the described construction and arrangement. the combustionk gasesgenerated in the lower portion of .the furnace chamber ilow lupwardly inthe combustion chamber with the greatest quantity, and the hottest,gases concentrating in the middle of the furnace. The resistf ancecaused by the walls retard the flow of gases along i special YnoseVlbaflle .formationin varyingllthefheating gas ywardly through thecentral portion of the furnace.

the sides of the chamber with the resulting tendency for the gases totake the path of least resistance and ow up- This uneven combustion gasflowand gas temperature distribution tends to continue during the gasflow vlaterally through the convection heating pass 26 'and wouldresultin undesirable heat transfer conditions throughout the convectionheating pass. However, in accordance with my invention, a projectingnose arch or baie '17 is provided at the throat section'24, and .thistogether with an arrangement of tubes in the-tube bank 13provides a tlgreaterresistance to combustion gas owfin thecentral portion of thefurnace andconvectionheating'gas.pass, Y Vwhich causes vsome of :thecombustiong'ases inlthecen- 3 tral portion of the furnace and convectionheating gas pass to flow towards the sides thereof.

The nose arch 17 is formed by a forward projection of the tubes alongthe rear wall 8 beyond the plane of the tube portions 16 which forms inhorizontal crosssection a symmetrical trapezoid, the sides of which aresubstantially parallel to the front walls 3,`4 and 5." This projectingstructure, or nose arch 17, may be constructed `of special tubes in sucha way as to allow the gases to pass between the tubes,lor as shown, bycovering or lining the tubes withrefractory material, be made in theform of a solid gas directing baffle.

The bank of steam generating tubes 13 is composed of the four tube rowgroups 18 and 19 adjacent the sides of the convection heating pass andadjacent tubes bent forwardly to various degrees to form a seven tuberow group 20 in the central portion of the pass. This arrangement aidsin directing the gas flow towards the opposite sides of the heating passdue to the higher resistance to gas flow offered by the seven tube rowarrangement inthe central portion compared to the four tube rowconstruction at the sides.

The tube clearance between the superheater tubes transversely to the gasllow direction could also be made closer in the central area of highcombustion gas` temperatures. This would increase the gas flowresistance in that area and deflect some of the hotter gases towards tthe sides of the heating pass.

Deflecting combustion gases away from the central portion of the`furnace causes an increase in gas flow along the sides of the furnacechamber outlet `and a mixing of the hotter and cooler gases in thoseareas so that the resultant gas flow through the convection heating passis more homogeneous. When used in conjunction with the describedarrangement of convection heated generating tubes and/or superheatngtubes for providing a greater gas flow resistance in the central portionof the convection heating pass, the heat transfer throughout the heatingpass will be more efficient and the danger of tube :failures due tolocalized hot combustion gases will be minimized;

While in accordance with the provisions of the statutes l haveillustrated and described herein the best form of the invention known tome, those skilled in the art will understand that changes may be made inthe form of the apparatus withoutdeparting from the spirit of theinvention covered by my claims` and that certain features of myinvention may sometimes be used to advantage without a corresponding useof other features.

What is claimed is:

l. A fluid heating unit comprising walls defining a vertically elongatedfurnace chamber and a laterally extending convection heating passopening through the rear of said furnace chamber, said walls includingopposed substantially vertical front and rear furnace chamber walls, abank of vertically extending fluid heating tubes positioned in saidconvection heating pass and extending across the width thereof, meansfor burning fuel in the lower portion of said furnace chamber andproducing a heating gas flow upwardly therein and thence laterallythrough said convection heating pass, and means for effecting asubstantially uniform temperature and transverse distribution of thegases flowing from said furnace chamber into said convection heatingpass comprising an arch projecting inwardly from said rear wall andcooperating with said front wall to define a restricted heating gas owpassage opening at its upper end to the furnace chamber space whereinthe gas turns into said convection heating pass, said arch having a`central nose portion formed by laterally aligned tubes and projectinginwardly to` a greater extent than its side portions, said arch beingspaced from said front wallla distance sutilcient to provide a heatinggas ow area in the central porl tion of said gas flow passage`ajlproximating but smaller than the heating gas flow area at the sidesthereof `to create a greater resistance to flow in the central portionof said gas passage than at the sides.

2. A fluid heating unit comprising walls defining a vertically elongatedfurnace chamber and a laterally extending convection heating passopening through the rear of said furnace chamber, said walls includingopposed substantially vertical front and rear furnace chamber walls,` abank of vertically extending fluid heating tubes positioned in saidconvection heating pass and extending across the width thereof, meansfor burning fuel in the lower portion of said furnace chamber andproducing a heating gas flow upwardly therein and thence laterallythrough said convection heating pass, and means for effecting asubstantially uniform temperature and transverse distribution of thegases flowing from said furnace chamber into said convection heatingpass cornprising an arch projecting inwardly from said rear wall andco-operating with said front wall to define a restricted heating gasflow passage opening at its upper end to the furnace chamber spacewherein the gas turns into said convection heating pass, said archhaving a central nose portion of trapezoidal formation in horizontalcross-section projecting inwardly to a greater extent than its sideportions, said arch being spaced from said front wall a distancesufficient to provide a heating gas flow area in the central portion ofsaid gas flow passage approximating but smaller than the heating gasflow area at the sides thereof to create a greater resistance to flow inthe central portion of said gas passage than at the sides.

3. A tiuid heating unit comprising walls defining a vertically elongatedfurnace chamber and a laterally extending convection heating passopeningthrough the rear of said furnace chamber, said walls including opposedsubstantially vertical front and rear furnace chamber walls, a bank ofvertically extending fluid heating tubes positioned in said convectionheatingpass and extending across the width thereof, means for burningfuel in the lower portion of said furnace chamber and producing aheating gas ow upwardly therein and thence laterally through saidconvection heating pass, and means for effecting a substantially uniformtemperature and transverse distribution of the gases flowing from saidfurnace chamber into said convection heating pass comprising an archprojecting inwardly from said rear wall and cooperating with said frontwall to define a restricted heating gas flow passage opening at itsupper end to the furnace chamber space wherein the gas turnsv into saidconvection heating pass, said arch having a central nose portion oftrapezoidal formation in horizontal crosssection projecting inwardly toa greater extent than its side portions, said arch `beingsnaced fromsaid front wall a distance sufiicient to provide a heating gas ow areain the central portion of said -gas flow passage approximating rbutsmaller thanthe heating gas liow area at the sides thereof to create agreater resistance to flow in the central portion of said gas passagethan at the sides, said front wall including vertical portions parallelto sides of the vcentraljnose portion of said arch.

4. A fluid heating unit comprising walls defining a vertically elongatedfurnace chamber and a laterally extending convection heating passopening through the rear `of said furnace chamber, said walls includingopposed substantially vertical front and rear furnace chamber walls,`abank'of vertically extending uid heating tubes postionedin saidconvection heating pass and extending across the widthethereof, some ofsaid tubes extending further toward the; furnace chamber in the centerpart` of the convection heating pass than those at `the sides thereof,means forburning fuel in the lower portion of said furnace chamber andproducing a heating gas flow upwardlytherein and thence laterallythrough said convection heating pass, and means for effecting asubstantially uniformtemperature and transverse distribu-` tion of thegases flowing from said furnace chamber into said convection heatingpass comprising an arch projecting inwardly from said rear wall andcooperating with said front Wall to dene a restricted heating gas flowpassage opening at its upper end to the furnace chamber space whereinthe gas turns into said convection heating pass, said arch having acentral nose portion formed by laterally aligned tubes and'projectinginwardly to a greater extent than its side portions, said arch beingspaced from said front wall a distance suicient to provide a heating gasow area in the central portion of said gas ow passage approximating ,butsmaller than the heating gas ow area at the sides thereof to create agreater resistance to ow in the central portion of said gas passage thanat the sides.

References Cited in the le of this patent UNITED STATES PATENTS

